Abstract
Pancreatic mucinous cystic neoplasms have a potential for malignancy, and surgical resection is usually recommended. Therefore, long-term follow-up of this disease is rarely reported. We experienced a case of mucinous cystic neoplasm in which the appearance and size of the cyst changed markedly during five years of follow-up. A simple cyst of 24 mm in diameter was detected occupying the body to the tail of the pancreas of a woman in her 50s who complained of left upper abdominal pain. The communication between the cyst and the main pancreatic duct was revealed with endoscopic retrograde pancreatography, and the main pancreatic duct dilatation at the upper stream of the cyst was detected by magnetic resonance pancreatography. The cyst was initially suspected to be an intra-ductal papillary mucinous neoplasm. Pancreatic juice cytology was negative, so the cyst was followed-up with ultrasonography every three month. During the follow-up period, the size of the cyst remained around 15 to 20 mm, but transient enlargement was observed accompanied with symptoms of acute pancreatitis. So that it was also suspected to be a pseudo cyst caused by pancreatitis. Five years later, a septum was first detected in the cyst, and after that pleural septa appeared. On contrast-enhanced ultrasonography, the septa within the cyst were strongly enhanced, and the so-called cyst-in-cyst appearance, a characteristic finding of a mucinous cystic neoplasm, was clearly visualized. Moreover, virtual sonographic cystoscopy reconstructed from the volume data depicted the cyst as having a smooth internal surface without any nodules. Both of these techniques were very useful for diagnosis of this case as a benign mucinous cystic neoplasm. After surgical resection, the lesion was pathologically confirmed to be a mucinous cystic neoplasm with moderate dysplasia.
